Recently, semiconductor integrated circuits have been further integrated so that LSI and VLSI can be practically utilized. Simultaneous with this tendency, the minimum pattern on the integrated circuit now has a size in the submicron region and finer. In the formation of a fine pattern, it is essential to use a lithography technique comprising covering a base or substrate to be fabricated, having a film formed thereon with a resist, then selectively exposing the same to form a latent image of a desired pattern, thereafter, developing the latent pattern to form a resist pattern, successively, conducting dry etching such that the resist pattern is used as a mask, followed by removing the resist, whereby a desired pattern is obtained. As the exposing source used in this lithography, ultraviolet light rays such as g-line (wave length of 436 nm) and i-line (wave length of 365 nm) have been used. However, as a pattern becomes finer, far ultraviolet light, vacuum ultraviolet light, electron beam, X ray, etc., which have shorter wavelengths, have been utilized. Particularly, recently, excimer laser (KrF laser having a wave length of 248 nm, ArF laser having a wave length of 193 nm) has become available as a light source and is expected to be effective in the formation of a fine pattern. In the specification of the present application, the term "radiation" includes light from these various light sources, i.e., ultraviolet light, far ultraviolet light, vacuum ultraviolet light, electron beam (EB), X ray, various kind of laser beam, etc.
In order to form a submicron pattern using an exposure light in the region of far ultraviolet light or vacuum ultraviolet light having a shorter wave length, a resist is required to have an excellent transparency at the wave length of the exposure light. Further, it is demanded to have an adequate dry etching resistance for utilization as a resist. Such a resist is, for example, a radiation-sensitive material characterized by comprising a polymer or copolymer of an acrylate or .alpha.-substituted acrylate having an adamantane skeleton in the ester portion thereof, which has been invented by the present inventors (see, Japanese Unexamined Patent Publication (Kokai) No. 4-39665). Further, the present inventors have invented, as a similar resist, a chemical amplification radiation-sensitive material characterized by comprising a polymer or copolymer of an acrylate or .alpha.-substituted acrylate having a norbornene skeleton in the ester portion thereof (see, Japanese Unexamined Patent Publication (Kokai) No. 5-257181) as well as a chemical amplification radiation-sensitive material comprising a polymer or copolymer of cyclohexylmaleimide (see, Japanese Unexamined Patent Publication (Kokai) No. 5-257285).
The chemical amplification radiation-sensitive materials as mentioned above have problems of low solubility in an aqueous alkaline solution, which is the developer, and poor adhesion. Thus, in order to solve these problems, the present inventors have found a pattern formation method, comprising adding isopropyl alcohol to an aqueous organic alkaline solution as a developer, and filed the patent application (Japanese Patent Application No. 6-276597, filed on Nov. 10, 1994).